External Iterator vs Internal Iterator

Question

What is an external and internal iterator in Java ?

Answer 1

External Iterator

When you get an iterator and step over it, that is an external iterator

for (Iterator iter = var.iterator(); iter.hasNext(); ) {
  Object obj = iter.next();
  // Operate on obj
}

Internal Iterator

When you pass a function object to a method to run over a list, that is an internal iterator

var.each( new Functor() {
  public void operate(Object arg) {
    arg *= 2;
  }
});